This application is a continuation of and claims priority from PCT/FR98/01462, which was filed on Jul. 8, 1998 and which published in French on Jan. 21, 1999, which in turn claims priority from French Application Nos. 97/09,115 filed on Jul. 11, 1997 and 97/09,663 filed on Jul. 24, 1997.
The subject of the present invention is a DNA sequence encoding drosomycin, a chimeric gene containing it, a vector containing the chimeric gene and a method of transforming plants and the disease-resistant transformed plants.
There is nowadays an increasing need to make plants resistant to diseases, in particular fungal diseases, in order to reduce or even avoid the need to resort to treatments with antifungal protection products, so as to protect the environment. One way of increasing this resistance to diseases consists in transforming plants so that they produce substances capable of providing their defence against these diseases.
Various substances of natural origin, in particular peptides, are known which have bactericidal or fungicidal properties, in particular against fungi responsible for plant diseases. However, the problem consists in finding such substances which not only can be produced by transformed plants, but can still preserve their bactericidal or fungicidal properties and confer them on the said plants. For the purposes of the present invention, bactericide or fungicide is understood to mean both the actual bactericidal or fungicidal properties and the bacteriostatic or fungistatic properties.
Drosomycins are peptides produced by the larvae and adults of drosophila by induction following septic injury or the injection of a low dose of bacteria. A peptide has already been described as having certain antifungal and antibacterial properties in vitro, in particular in French patent application 2,725,992, where the peptide is obtained by induction in drosophila and purification. The gene encoding this same peptide has also been described by Fehlbaum et al. (1994). The possibility of integrating this gene into a plant to confer on it resistance to diseases of fungal or bacterial origin has, however, so far not been described.
It has now been found that the genes for drosomycins could be inserted into plants to confer on them properties of resistance to fungal diseases and to diseases of bacterial origin, providing a particularly advantageous solution to the problem set out above.
The invention concerns a chimeric gene containing a DNA sequence coding for drosomycin, a vector containing the chimeric gene, a method for transforming plants and the resulting transformed plants. The drosomycin produced by the plants provides them with resistance to diseases, in particular of fungal origin.